Abstract

Cigarette smoke, a major risk factor in emphysema, causes cell death by incompletely understood mechanisms. We demonstrated cigarette smoke extract (CSE) induced caspases activation in human lung fibroblasts (MRC-5 cells). PKCeta was activated in MRC-5 cells exposed to CSE, translocated from cytosol to membrane fraction.The aim of this study was to investigate the involvement of protein kinase Ceta activation in CSE induced extrinsic apoptotic pathway. Lactate dehydrogenase (LDH) release was measured using a cytotoxicity detection kit. Colorimetric MTT assay was used as a measure of cell viability. Overexpression of wild-type (wt) PKCetadecreased cell viability, as assessed by colorimetric MTT assay in MRC-5 cells exposed to 20% CSE for >12 h compared to the LacZ-infected MRC-5 cells.LDH release following CSE exposure was significantly increased inwtPKCetainfected MRC-5 cells compared to the control. We demonstrated that CSE induced expression of caspases-3/caspase-8 cleavage by Western immunoblot analysis in MRC-5 cells and wt PKCeta significantly increased expression of caspases-3/caspase-8 compared to the control LacZ. On the other hand, dominant-negative (dn) PKCeta inhibited apoptosis in MRC-5 cells exposed to CSE showing decreased expression of caspases-3/caspase-8 compared to the control LacZ. PKCeta activationplays a role in the extrinsic apoptotic pathway of MRC-5 cells induced by CSE. These results suggest thatmodulation of PKCetamayhave therapeutic potential in the prevention of smoke-related lung injury.